I'm really captured by the idea of PeerTube - would it be okay for me to unofficially reupload some of the YT videos there? Could we license them under CC-BY-SA or something to make these things simpler?

Atahualpa is in charge of the videos, right? Are you by any chance reading this, Atahualpa? Okay or not okay?

No objections from my side. I'll have a look at the video licenses on YouTube when uploading the WIP videos for the current release.